A new series of cyanide-bridged heterobimetallic FeIII–FeIII/MnIII/CuII one-dimensional complexes: synthesis, crystal structures, and magnetic properties

Abstract

The trans-dicyanide-containing precursor K[Fe(bpdBrb)(CN)₂]·2H₂O (1) (bpdBrb²⁻ = 1,2-bis(pyridine-2-carboxamido)-4,5-dibromobenzenate) and four transition metal compounds containing Fe^III, Mn^III or Cu^II have been employed as building blocks to assemble cyanide-bridged systems, resulting in a series of new cyanide-bridged single chain complexes [Fe(bpdBrb)(CN)]_n·nCH₃OH (2), {[Mn(L¹)][Fe(bpdBrb)(CN)₂]}_n·nCH₃CN (3), {[Mn(L²)][Fe(bpdBrb)(CN)₂]}_n·2nH₂O (4) and {[Cu(cyclam)][Fe(bpdBrb)(CN)₂] ClO₄}_n·nCH₃OH (5) (L¹ = 5-Brsalpn and L² = 5-Clsaltn). Single crystal X-ray diffraction analysis reveals the rare one-dimensional “shish-kebab” neutral structure of complex 2 with bpdBrb²⁻ as the equatorial ligand and single cyanide ligands as axial bridges. The other three cyanide-bridged complexes can be structurally characterized as the neutral one-dimensional chains (2 and 3) consisting of alternating units of [Mn(L)]⁺ (L = L¹ or L²) and [Fe(bpdBrb)(CN)₂]⁻ and a cationic one-dimensional single chain (4) consisting of the repeating units {NC-[Fe(bpdBrb)]-CN-Cu(cyclam)⁺} with free ClO₄⁻ as the counter-anion. Investigation of the magnetic properties of the four 1D chain complexes reveals the antiferromagnetic coupling between neighbouring low spin Fe(III) ions in complex 2 and the ferromagnetic interaction between the cyanide-bridged Fe(III)–Mn(III)/Cu(II) ions in complexes 3–5. By employing infinite chain models or a MAGPACK program, the magnetic susceptibilities of these complexes were simulated, leading to the magnetic coupling constants J = −1.98(2) cm⁻¹ for 2, J₁ = 0.56(1), J₂ = 0.45(2) cm⁻¹ for 3, J₁ = 0.59(3), J₂ = 0.43(8) cm⁻¹ for 4, and J = 1.77(5) cm⁻¹ for 5.